1. Field of the Invention
The present invention relates to a filtering system and, more particularly, to a filter backflushing system for removing contaminants from a filter element, the backflushing system includes a bladdered accumulator for providing a high pressure rapid burst of backflush fluid stored within the accumulator in a reverse flow through the filter element.
2. Brief Description of the Prior Art
A filtered supply of a coolant, lubricant, fuel, water or other fluid is oftentimes essential for the proper operation and maintenance of a multitude of industrial automotive and commercial systems. Unfortunately, the filter elements utilized to filter such fluids must be periodically replaced or cleansed to remove a clogging accumulation of contaminants and foreign matter therefrom.
The periodic removal and replacement of a clogged filter element generally requires the shutting down of an associated system during the replacement procedure. The expensive, nonproductive downtime of the filtration and associated systems, the replacement cost of the filter element and the expenses incurred to properly dispose of the soiled filter element and the contents thereof in accordance with the ever increasing degree of governmental and environmental mandates, have led to the development of numerous integrated filter element cleansing systems.
One type of integrated system, generally termed backflushing or backwashing, generates a reverse flow of fluid through individual filter elements to dislodge the contaminants therefrom, wherein the backflushing fluid has been filtered by a singular filter or multiple filters. Advantageously, backflushing reduces the operational cost of filtering and associated systems by extending the usable life of the filter elements, by reducing the systems"" downtime required to replace filter elements and by reducing disposal costs.
In U.S. Pat. No. 5,374,351, a filter backflushing system is provided. The filtration system includes either a pneumatically-driven piston or pneumatic accumulator for propelling a high pressure backflush fluid through the system in a reverse direction. This reverse backflush flow then removes contaminants from a filter element. An external pneumatic system provides replenishing air pressure to the piston or accumulator, allowing its continued operation. Air replenishment is needed in non-pistoned accumulators because in the accumulator pressurized air becomes entrained with the backflushing fluid and this pressurized air is lost during the backflushing operation. In a pistoned accumulator, replenishment is needed to repressurize the piston chamber and replace any air which blows by the piston area, thus becoming entrained in the backflushing fluid. Similarly, in U.S. Pat. No. 5,846,420, an external pneumatic system provides replenishment air pressure to a piston arrangement, allowing a pressurized backflushing operation. While such systems work very satisfactorily, there is always a desire to improve upon their operation.
In this regard there is a desire to eliminate the requirement for a separate air replenishment system supporting the backflushing operation. Also, there is a desire to eliminate the possibility of entrained air in the backwash fluid. By doing so, the backwashed filters will not be exposed to a fluid composition not normally used in regular operations.
An object of the present invention is to provide a filter backflushing system having a bladder-type accumulator which supplies a short duration, high intensity backflushing flow through a filter element.
A further object of the present invention is to provide a filter backflushing system which supplies a regulated backflushing flow through a filter element.
A still further object of the present invention is to provide a filter backflushing system which is highly suited for effectively and efficiently removing contaminants in virtually any type of filtration system.
A still further object of the present invention is to provide a self-contained filter backflushing system independent of an air or pressurized replenishment system.
A still further object of the present invention is to provide a filter backflushing system which uses filtered fluid in a backflushing operation.
A still further object of the present invention is to provide a filter backflushing system which can also use a specialized backflush material for specific applications.
To attain these objectives, there is provided a filter backflushing system which includes a filter housing enclosing a removable filter element, a valve controlled feed pipe for introducing an unfiltered fluid into the filter housing, a valve controlled output feed pipe for removing filtered fluid from the filter housing, a backflushing fluid accumulator enclosing a bladder which stores a portion of the filtered fluid, an accumulator charging pump for providing pressurized filtered fluid from a portion of the outlet feed pipe to the accumulator, and an actuator responsive to system fluid pressure.
The bladder of the accumulator containing backflushing liquid is effectively isolated by a membrane which contains a compressible inert gas in the remaining volume of the backflush fluid accumulator. Preferably, the minimum bladder volume of the backflushing fluid accumulator is substantially equivalent to the filter housing volume, thus allowing the clean, filtered fluid contained within the backflushing fluid accumulator to completely displace the fluid within the filter housing during the backflushing operation. A complete displacement would substantially remove all of the flow reducing contaminants and foreign matter which have clogged the filter element.
In response to an actuating signal, the bladder can rapidly de-compress within the interior of the backflushing fluid accumulator. This rapid de-compression, assisted by the compressed inert gas between the membrane of the bladder and the interior accumulator wall, propels the filtered fluid contained within the accumulator in a reverse direction through the filtering system. The compression force of the bladder produces a high, constant fluid pressure within the filter backflushing system which effectively backflushes the filter element. The backflushing flow may be regulated in accordance with the requirements of the filter, the types of fluids flowing through the filtration system or other parameters. In particular, the backflushing flow intensity may be regulated by altering the relative expansion capacity of the bladder, use of restrictive flow orifices in the backflush feed pipe varying the output pressure of the accumulator charging pump, or adjusting the actuation signal.
The direction of fluid flow through the filter backflushing system is controlled by a plurality of suitably positioned pneumatically controlled valves. In particular, the accumulator pump input and output feed pipes for isolating the accumulator pump, the feed pipe for inputting the solid/fluid mixture into the interior of the filter element, the backwash feed pipe for supplying backwash fluid from the accumulator to the filter element, the outlet feed pipe for discharging filtered fluid from the filter element and the drain output for removing fluid from the filter housing, each include a valve which is adapted to selectively shut off or enable the flow of fluid therethrough during the normal filtering and backflushing operations of the filter backflushing system.
During normal filtration, a solid/fluid mixture enters the filter element through the input feed pipe, thereby allowing the solid and fluid mixture to be separated by the filter element. The filtered fluid enters the output feed pipe disposed proximate the top of the filter housing. The filtered fluid contained within the output feed flows on to systems supported by the filtration system. A small portion of the filtered fluid branches off the output feed and is further pressurized by the accumulator charging pump. The accumulator charging pump discharges the pressurized filtered fluid to the backflushing fluid accumulator compressing the bladder contained within.
During the backflushing operation, the direction of fluid flow is reversed in regard to the filtration mode. First, the accumulator charging pump input, the accumulator charging pump output, the output feed pipe, and feed pipe control valves are closed simultaneously or in rapid succession. The accumulator charging pump is deactivated immediately before or after the valve closure. Subsequently, the drain output control valve and backflush feed control valve are opened, allowing the backflushing fluid to flow from the bladder of the accumulator onto the filter housing in a purging action. Once the bladder reaches the end of its capacity or the pressure of the backflush feed decreases to a preset point, the drain output control valve and backflush feed control valve are closed. The output feed pipe, feed pipe accumulator charging pump input, and accumulator charging pump output control valves are then reopened. Upon activation of the accumulator charging pump the system is returned to a condition for a normal filtering operation.